Method of protecting plants from cold injury

ABSTRACT

A method of reducing cold injury or damage to plants such as peanut, citrus trees, peaches, strawberries and other plants susceptible to cold injury such as frost or freezing comprises applying a pyridylaniline active agent such as fluazinam to the plant in an amount effective to reduce cold injury to the plant.

FIELD OF THE INVENTION

The present invention concerns methods of protecting plants such ascitrus trees, peanuts, peaches and strawberries from cold injury, suchas damage by frost or freezing.

BACKGROUND OF THE INVENTION

Frost, freeze and other cold damage to plants is a serious agriculturalproblem. Plants that flower early in the growing season are susceptibleto late winter or early spring frost, and plants that are harvested latein the growing season are susceptible to late fall or early winterfrost. It has been estimated that approximately 1.5 billion dollarsworth of agricultural products are annually lost to freezingtemperatures in the United States alone (see U.S. Pat. No. 5,276,006).Among other things, frost injury causes significant damage to citrus,strawberry, peanut and peach crops. Accordingly, there is a need for newways to combat frost injury to plants.

A variety of approaches to protecting plants from frost and freezinghave been suggested. For example, U.S. Pat. No. 5,276,006 to Shin et al.(assigned to Great Lakes Chemical Corp.) describes an aqueous plantcryoprotectant containing a tetrahydrofurfuiryl alcohol ortetrahydrofurfuryl amine. U.S. Pat. No. 4,207,091 to Fischer (assignedto Ciba-Geigy Corp.), describes a method of combating frost damage inplants by treating the plants prior to frost with certain hydroxamicacid derivatives. U.S. Pat. No. 4,432,160 to Lindow (assigned to theUniversity of California) suggests inhibiting frost damage by treatingplants with antagonistic ice nucleation deficient bacteria to inhibitcolonization of the plant by ice nucleation capable bacteria. U.S. Pat.No. 5,133,891 to Barr et al. (assigned to Rhone Poulenc AG Co.),describes a method for combating frost damage by applying aluminumtris-[O-ethyl phosphonate], or fosetyl-Al, apparently to kill icenucleating bacteria. Nevertheless, there remains a need for new ways totreat plants to reduce damage from frost and freezing.

SUMMARY OF THE INVENTION

The present invention provides a method of reducing cold injury ordamage to a plant, including individual plants and plants existing as acrop of like plants. The method comprises applying a pyridylanilineactive agent to the plant in an amount effective to reduce cold injuryto the plant. A particularly preferred active agent is fluazinam. Themethods may be carried out to reduce any type of cold injury, includingfrost injury and freezing injury.

The present invention is explained in greater detail below. Thisexplanation is not intended to be an exhaustive catalog of all thedifferent embodiments and manners in which the present invention may becarried out, but is intended to be illustrative of particularembodiments of the invention. Numerous variations will be apparent tothose skilled in the art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention may be used to protect any type of plant fromfrost or freeze injury, including trees, shrubs, herbaceous plants, etc.Plants treated by the invention are typically frost or cold sensitiveplants, in that they are susceptible to frost, freezing or cold damageor injury in economically or aesthetically significant amounts. Specificplants that may be protected by the method of the invention include, butnot limited to, peanuts, peaches, strawberries, citrus trees (lemon,lime, orange, etc.), cherries, apples, etc, as well as vegetable crops(e.g., beans, peas), as well as ornamental plants. The term “plant” asused herein includes the complete plant or a portion thereof, such as aflowers, fruits, leaves, stems vegetables, roots, tubers, etc. “Alkyl”as used herein refers to an alkyl group, which may be linear orbranched, and saturated or unsaturated. Alkyl groups, as used herein,are preferably saturated.

“Lower alkyl” as used herein refers to an an alkyl group which contains1 to 4 carbon atoms.

“Alkoxy” as used herein refers to a group —O—R, wherein R is alkyl.

“Lower alkoxy” as used herein refers to an alkoxy group which contains 1to 4 carbon atoms.

“Halogen” as used herein refers to any halogen group, such as fluoro,chloro, bromo, or iodo, preferably chloro.

“Cold injury” means any type of injury to a plant or plant part causedby a decrease in temperature that results in an economic or aestheticdamage to that plant. Such injury may be by frost injury, freezinginjury, or a decrease in temperature below that tolerated by the planteven if the temperature does not decrease below freezing (32° F.; 0° C.)(e.g., as seen in orchids).

“Frost injury” as used herein refers to any type of damage to a plant orplant part that results from the deposition of frost on the surfacethereof, whether that frost is natural frost or frozen water or watervapor deposited upon the plant or plant part by artificial means. Suchdamage includes, but is not limited to, reduced yield, blemishes orother damage that decreases the quality or value of the plant or plantpart without reducing yield, etc.

“Freeze injury” as used herein refers to any type of damage to a plantor plant part that results from the formation of ice crystals in atleast some cells of that plant, whether or not the ice crystals areformed by natural means due to decreased ambient temperature orartificial cooling or refrigeration. Again, such damage includes, but isnot limited to, reduced yield, blemishes or other damage that decreasethe quality or value of the plant or plant part without reducing yield,etc.

Active compounds that may be used to carry out the present inventionare, in general, pyridylanilines of Formula I:

wherein X is a trifluoromethyl group, a halogen atom, a lower alkylgroup or a lower alkoxy group; n is an integer of 0 to 4; R is ahydrogen atom or an acetyl group; Y is a hydrogen atom, a halogen atom,a lower alkoxy group, a lower alkylthio group, a hydroxy group, an azidogroup or a phenoxy group of which the phenyl ring may be substituted bya hydroxy group; and Z₁, Z₂, and Z₃ are independently a trifluoromethylgroup or a nitro group; provided that at least one of X is atrifluoromethyl group or a lower alkyl group when n is an integer of 3or 4.

Preferred compounds of Formula I are those wherein X is atrifluoromethyl group, a halogen atom, a lower alkyl group or a loweralkoxy group; n is an integer of 1 to 4; R is a hydrogen atom or anacetyl group; Y is a hydrogen atom, a halogen atom, a lower alkoxygroup, a lower alkylthio group or a hydroxy group; Z₁, Z₂, and Z₃ are atrifluoromethyl group or a nitro group, with the proviso that at leastone X is trifluoromethyl and with the proviso that when the Xsubstitution pattern is 3-chloro-5-trifluoromethyl, Y in additionoptionally is azido or 2, 3, or 4-hydroxyphenoxy.

Compounds of Formula I are known, and can be made as described in U.S.Pat. No. 4,331,670 to Nishiyama et al. It is specifically intended thatall United States patent references cited herein be incorporated hereinby reference.

A particularly preferred active compound for carrying out the presentinvention is fluazinam (or3-chloro-N-[3-chloro-2,6-dinitro-4-trifluoromethyl)phenyl]-5-trifluoromethyl-2-pyridinamine)(See Merck Index No. 4153 (12th Ed. 1996)), which has the structure ofFormula II:

Compounds of Formula II may be made in the same manner as compounds ofFormula I above.

Active compounds used herein may be formulated together withagricultural adjuvants and/or carriers into various forms such as dusts,granules, water dispersible granules, wettable powders, emulsifiableconcentrations, suspension concentrates, soluble concentrates, watersoluble powders, flowables, aerosols or pastes, ultra low-volumeformulations, etc. When such formulations are to be actually used, theymay be used as is or after being diluted with suitable diluents orcarriers such as water.

Such formulations may be composed of 0.01 or 0.1 to 90 or 99 parts byweight of active ingredient, 0.0 or 0.1 to 99.9 parts by weight ofagricultural adjuvants, and 0.0 or 0.1 to 99.9 parts by weight ofagricultural carrier.

Suitable adjuvants include, but are not limited to, emulsifiers,suspending agents, dispersants, extenders, penetrating agents, wettingagents, thickeners or stabilizers, stickers, combinations of theforegoing, etc. They may be combined with the active agents as the caserequires.

The carriers that may be used to carry out the present invention may beclassified into solid carriers and liquid carriers. Solid carriersinclude, but are not limited to, powders of animal and plant origin suchas starch, activated carbon, soybean flour, wheat flour, wood powder,fish powder or powdered milk; or mineral powders such as talc, kaolin,bentonite, calcium carbonate, zeolite, diatomaceous earth, white carbon,clay, alumina; combinations of the foregoing; etc. Liquid carriersinclude, but are not limited to, water, alcohols such as isopropylalcohol or ethylene glycol; ketones such as cyclohexanone or methylethyl ketone; ethers such as dioxane or tetrahydrofuran; aliphatichydrocarbons such as kerosene gas oil or the like; aromatichydrocarbones such as xylene, trimethylbenzene, tetramethylbenzene,methylnaphthalene or solvent naphtha; halogenated hydrocarbons such aschlorobenzene, acid amides such as dimethylacetamide; esters such asglycerine ester of a fatty acid; nitrites such as acetonitrile; orsulfur-containing compounds such as dimethyl sulfoxide; combinations ofthe foregoing; etc.

The active compounds described herein may be used alone or incombination with other active compounds such as insecticides, miticides,nematicides, fungicides, antiviral agents, attractants, herbicides orplant growth regulators, as desired. Such other compounds include, butare not limited to, those set forth in U.S. Pat. No. 5,360,806 at column12, line 25 to column 18, line 8.

The active compounds described herein are applied as an activeingredient concentration of from 0.1 to 500,000 ppm, preferably from 1to 100,000 ppm. The active ingredient concentration may optionally bechanged depending upon the formulation, the manner, purpose, timing orplace of the application, and the condition of the plants and risk offrost or freeze damage.

The amount of the application of the active ingredient per unit surfacearea is usually from about 0.1 to 5,000 g, preferably from 10 to 1,000g, per hectare. However, in some cases, the amount of the applicationmay be outside this range.

Various formulations containing the compounds of the present inventionor their diluted compositions may be applied to plants by conventionalmethods for application, including but not limited to spraying (e.g.,spraying, jetting, misting, atomizing, powder or grain scattering ordispersing in water), soil application (e.g., mixing or drenching),surface application (e.g., coating, powdering or covering),impregnation; etc. The applying step may be carried out by a so-calledultra low-volume application method, in which the composition orformulation applied consists essentially of the active agent.

Active agents may be applied as a salt with an acidic substance or abasic substance. The salt with an acidic substance may be an inorganicsalt such as a hydrochloride, a hydrobromide, a phosphate, a sulfate, anitrate, etc. The salt with a basic substance may be a salt of aninorganic or organic base, such as a sodium salt, a potassium salt, acalcium salt, an ammonium salt or a dimethylamine salt.

Fluazinam is, advantageously, rapidly and extensively degraded in theenvironment. The field soil dissipation half-life ranges from 6 to 49days. The low seasonal use rate limits the amount of product in theenvironment. The aerobic aquatic half-life is 18 to 26 hours whereextensive degradation leads to a large number of degradates. Due tofluazinam's low water solubility (0.071 ppm at pH 7) and high soiladsorption (Koc ranging from 1700 to 2300), it has very low potential toleach to ground water. While fluazinam can reach surface water viarun-off or drift, the rapid and extensive degradation makes it extremelyunlikely that fluazinam will persist in surface waters.

A preferred formulation of fluazinarn for use in carrying out thepresent invention is OMEGA 500F™ agricultural fungicide, which comprisesfluazinam (40.0%) and inert ingredients (60.0%), and contains 4.17pounds fluazinam per gallon 500 grams per liter. OMEGA 500F™agricultural fungicide is available from ISK Biosciences Corporation,5970 Heisley Road, Ste. 200, Mentor, Ohio 44060 USA. In use, OMEGA 500F™fungicide is applied with ground equipment in sufficient water to obtainadequate coverage of foliage. Gallons to be used will vary with crop andamount of plant growth. Spray volume usually will range from 20 to 60gallons per acre (200 to 600 liters per hectare) for dilute sprays and 5to 10 gallons per acre (50 to 100 liters per hectare) for concentrateground sprays. An example spraying rate for OMEGA 500F™ formulation isas set forth in Table 1 below.

TABLE 1 APPLICATION RATE AND TIMING USING INTEGRATED PEST MANAGEMENT(IPM) TECHNIQUES CROP RATE PER ACRE Peanut 1 pint APPLICATION DIRECTIONSApply with ground application equipment only, when vines are 6 inchesfrom touching and weather conditions are favorable according to theSclerotinia blight advisory. Make a second application if weatherconditions remain favorable, but not within 3 weeks of the first spray.A third application can be made if disease conditions remain favorablebut not within 3 weeks of the second application. DO NOT apply within 30days of threshing for harvest.

Plants may be treated individually or as crops of like plants planted inan agricultural field of such plants, in which case the crop is treatedas described above with respect to plants. Typically, the plants areharvested after they are treated, although the present invention may becarried out on plants that are not harvested (e.g. ornamental plants,particularly flowers). By “harvesting” is meant collection of the entireplant or a plant part such as a flower, leaf, stem, root, tuber, fruit,vegetable, etc. An advantage of the instant invention is the longduration of action of the active agent. Thus, the harvesting step may becarried out one week, one month, two months or more after the lastapplication of the active agent, with the active agent still beingeffective to reduce frost damage during the intervening period.

The present invention is explained in greater detail in the followingnon- limiting Examples.

EXAMPLE 1 Peanut Field Studies

A peanut field was fumigated on April 28 with Metam sodium to controlCylindrocladium. The test plants were planted on May 22 with 16different varieties of seed (Andru 93; Georgia Green; Tam Run 98; AT120;Southern Runner; Georgia Gold; Georgia Runner; 6K7WIDLEIL; FLA97R;FLAMDR98; FLA84×9B; NC7; VA93B; Perry; VA92R; VA98R), with a two-rowplanter. Temik and rhizobium were applied in furrow at standard rates.The spray date for the first treatment was July 20; the spray date forthe second treatment was August 19. A tractor-mounted sprayer was usedfor all treatment sprays, with three hollow-cone nozzles per row at 40psi, and 15 gal water/acre, at a height to cover the entire plant. Onlythe two treatment rows were sprayed. There were two unsprayed borderrows between each treatment, to minimize interplot interference, and toassure even distribution of disease across plots. Herbicides,insecticides, and early leafspot control were applied according tostandard practices across the field. Particular treatments were asfollows:

(1) untreated control

(2) 15.22 fl. oz. Omega 500™ fluazinam 500F/acre (per spray)

(3) 30.44 fl. oz. Omega 500™ fluazinam 500F/acre (per spray)

(4) 60.88 fl. oz. Omega 500™ fluazinam 500F/acre (per spray)

(5) 32.0 fl. oz. Rovral™ brand iprodione+7.68 fl. oz. Nufilm™ adjuvantper acre (per spray)

(Rovral™ is the trade name for iprodione (C₁₃ H₁₃ Cl₂ N₃ O₃) CAS #36734-19-7, a foliar fungicide which is the only currently registeredfungicide available to control Sclerotinia blight. Nufilm™ is anadjuvant that is recommended for use with Rovral™ ).

Frost occured on October 25. Frost ratings were done on November 2d.Rating Index: 1<5% green leaves, 4>50% green leaves; values between 1and 4 were scaled from 5 to 50%. Stems were not rated, and varied fromcompletely brown, to black, to bright green. When rating percentage ofgreen leaves in a plot, those obviously dead from disease were ignored,and the rating was based on the remaining leaves.

Peanuts were dug on November 10, and harvested on November 15. Moisturesamples were taken from untreated plots of each variety. Yields wereadjusted to 9% moisture.

Data: Statistics were run using the SAS System using the General LinearModels Procedure. Results are as set forth in Tables 2-7 below.

TABLE 2 Dependent Variable: Frost Injury Frost Mean Pr > F Model 0.0001Treatment 0.0001 Cultivar 0.0001 Treatment vs Cultivar 0.1971

The data set forth in Table 2 indicates that there was a treatmenteffect (fluazinam), and a cultivar effect, but not an interaction effectin respect to frost.

TABLE 3 Dependent Variable: Disease Incidence Disease Mean Pr > FTreatment 0.0001 Cultivar 0.0001 Treatment vs Cultivar 0.0586

The data set forth in Table 3 indicates that there was a treatmenteffect (fluazinam), and a cultivar effect, but not an interaction effectin respect to disease.

TABLE 4 Dependent Variable: Yield/Acre Yield/Acre Mean Pr > F Treatment0.0001 Cultivar 0.0001 Treatment vs Cultivar 0.0586

The data set forth in Table 4 indicates that there was a treatmenteffect (fluazinam), and a cultivar effect, but not an interaction effectin respect to yield per acre.

TABLE 5 Dependent Variable: Frost Injury Pr > |T| High Rate vs Control0.0001 High Rate vs Rovral 0.0001

The data set forth in Table 5 indicates that the high rate of fluazinamtreatment gave statistically significantly better frost protection ascompared to both the Untreated Control and the Rovral treatments.

TABLE 6 Dependent Variable: Disease Incidence. Pr > |T| High Rate vsControl 0.0001 High Rate vs Rovral 0.3911

The data set forth in Table 6 indicates that the high rate of fluazinamtreatment gave statistically significantly better disease control thanthe Untreated Control treatment, but not significantly better than theRovral treatment.

TABLE 7 Dependent Variable: Yield/Acre. Pr > |T| High Rate vs Control0.0001 High Rate vs Rovral 0.0001

The data set forth in Table 7 indicates that the high rate of fluazinamtreatment resulted in yields that were statistically significantlyhigher than both the Untreated Control and the Rovral treatments.

Discussion: Fluazinam significantly reduced frost injury and Sclerotiniablight on various peanut cultivars. Peanut cultivars varied in theirresistance to frost and disease injury. There was no interaction betweenfluazinam and cultivars regarding frost protection and disease.

Yields were significantly higher with fluazinam and some cultivars werehigher yielding than others. There were no interactions betweenfluazinam and cultivars regarding yield.

Fluazinam at the highest tested rate protected plants from frost. Theprotection was unrelated to disease control. Yield increases from use offluazinarn probably resulted from less frost injury. Some yield increasecould have resulted from undetected subterranean disease controleffected by fluazinam above and beyond Rovral control, however, in theprevious year's test in which no frost occurred there was nostatistically significant difference in yield between the treatments,which would tend to discount this possibility.

A significant observation was that there was a 66-day lapse between thelast treatment application and the frost event, and a 90-day lapsebetween the last treatment application and harvest. It is unlikely thatsignificant active compound was still present as the half life of thecompound is approximately 24 hours in inundated soils. Record rainsoccurred in this field during this intervening period creating extendedperiods of extremely wet conditions. Therefore, it is likely that thefrost protection was a systemic physiological response to the compoundrather than a direct effect on the compound on ice crystal formation.Another possible explanation is that some leaf surface microorganismsare known to affect ice crystal formation and hence, plant vulnerabilityto frost injury. Fluazinam application could have modified thepopulation to render it more protective than the native population. Thisexplanation seems unlikely, as the intervening period should haveallowed for the repopulation of the native leaf surface flora.

In summary, fluazinam has the potential to change peanut plants in sucha way as to reduce frost injury and affect a corresponding yieldincrease.

The foregoing is illustrative of the present invention, and is not to beconstrued as limiting thereof. The invention is defined by the followingclaims, with equivalents of the claims to be included therein.

That which is claimed is:
 1. A method of reducing cold injury to aplant, comprising applying fluazinam to said plant in an amounteffective to reduce cold injury to said plant.
 2. A method according toclaim 1, wherein said applying step is followed by the step ofharvesting said plant.
 3. A method according to claim 2, wherein saidharvesting step is carried out at least one week after said applyingstep.
 4. A method according to claim 2, wherein said harvesting step iscarried out at least one month after said applying step.
 5. A methodaccording to claim 2, further comprising the step of subjecting saidplant to frost between said applying step and said harvesting step.
 6. Amethod according to claim 1, wherein said applying step is carried outby spraying.
 7. A method according to claim 1, wherein said plant is apeanut plant.
 8. A method according to claim 1, wherein said plant is apeach tree.
 9. A method according to claim 1, wherein said plant is astrawberry plant.
 10. A method according to claim 1, wherein said plantis a citrus tree.
 11. A method of reducing frost injury to a plant,comprising applying fluazinam to said plant in an amount effective toreduce frost injury to said plant.
 12. A method according to claim 11,wherein said applying step is followed by the step of harvesting saidplant.
 13. A method according to claim 12, wherein said harvesting stepis carried out at least one week after said applying step.
 14. A methodaccording to claim 12, wherein said harvesting step is carried out atleast one month after said applying step.
 15. A method according toclaim 12, further comprising the step of subjecting said plant to frostbetween said applying step and said harvesting step.
 16. A methodaccording to claim 11, wherein said applying step is carried out byspraying.
 17. A method according to claim 11, wherein said plant is apeanut plant.
 18. A method according to claim 11, wherein said plant isa peach tree.
 19. A method according to claim 11, wherein said plant isa strawberry plant.
 20. A method according to claim 11, wherein saidplant is a citrus tree.